DE20219824U1 - Rotary machining tool such as drill for drilling holes has minimum wall thicknesses between defined upper and lower limits - Google Patents

Abstract

The drill has at least one swarf groove (1) and at least one web (2), and an internal cooling channel (3). The minimum wall thicknesses between the cooling channel (3) and the external surface (7) of the drill, between the cooling channel and the swarf carrying surface (5) and between the cooling channel and the surface (6) carrying no swarf lie in a region between lower and upper limits which depend on the diameter of the drill.

Description

The invention relates to a rotationally driven Chipping or Insert tool, in particular a drill, according to the preamble of the claim 1.

For coolant or lubricant supply have cutting tools on internal cooling channels, through which the coolant is directed to the drill tip. In addition to the function, the drill bit to cool or to lubricate comes the coolant also the function to improve the chip removal.

To transport the chips out of the chip flute must, especially in deep hole drilling, the coolant partly under high Pressure are supplied, wherein the internal cooling channel or the drill corresponding pressures destructively has to endure. It is just in the course of spreading Minimum quantity lubrication strives to design the cooling channels as large as possible. moreover there is a need to be able to create ever smaller and longer holes. With increasing length and decreasing diameter of the drilling tool but it is always more difficult, the internal cooling channels so too dimension that a corresponding coolant flow or coolant pressure is provided without the stability of the drill suffers. Because the size of the cooling channels is limited by the distance to the drill back or chip space. Too thin Jetties there are cracks and tool breaks. For multi-bladed insert tools have to the cooling channels as well have certain minimum distance from each other, otherwise impairments the drill bit geometry, i. e.g. the chisel edge or one Leaking be caused.

Known drills have mostly circular cut internal cooling channels. In addition, methods are already known in principle, with which sintered blanks can be produced with elliptical cooling channel cross-sections, for example from the DE 42 42 336 A1 , Also in the US patent US 2,422,994 is already mentioned by a deviating from the circular shape Kühlkanalprofilgebung. Also cooling channels with trigon profile in the form of an isosceles triangle with rounded corners have been proposed, for example in the Scriptures DE 199 42 966 A1 ,

In addition, in the DE 3629035 A1 already proposed a double cutter with a cooling channel profile in the form of an isosceles triangle with rounded corners, with a center near location of the internal cooling channels is to be made possible, which allows a central cooling channel supply at the conical end of the drill.

The object of the invention, on the other hand, is an internally cooled Cutting tool of the generic type with regard to coolant throughput, Fracture, compression, torsional and bending strength to improve.

This task is characterized by the features of claim 1.

The invention is the knowledge underlying that on the cooling channel occurring voltages of the shape of the cooling channel and thus mainly from the notch effect of the cooling channel at the smallest radii resulting in load direction. Further became recognized that for the resistance of an insert tool, such as a drill or cutters, can oppose these voltage spikes, i. for its stability and ultimately for this, whether it comes to cracking or premature breakage of the tool, next to the cooling channel occurring voltage spikes the distance of the cooling channels to the chip space and thus the Location of the cooling channel on the jetty is crucial.

FEM (finite element method) simulations revealed that in previously used circular Kühlkanalgeometrien Although small voltage spikes occur. Because of the essence circular segment However, webs can not optimally use the existing space in the dock be so that it comes to relatively small-area cooling channel cross-sections. Due to the resulting low flow rates, you come across it on limits regarding length and diameter of the drill.

On the other hand, in known Trigon profiles though higher Throughputs achieved. The approach, with trigonal cooling channel cross sections without Below a minimum wall thickness existing in the drill bit, circular segment Maximum utilization of space and thus increase throughput rates, leads however to extreme voltage peaks in the notch bottom of the cooling channel and thus to a reduced strength of the insert tool.

Extensive experiments and simulations led to the cross-sectional geometry according to the invention, ie minimum radii in the range of 0.35 to 0.9 times, in particular 0.5 to 0.85 times, preferably 0.6 to 0.85 times, particularly preferably 0.7 to 0.8 times, for example 0.75 times the radius of a circle enclosed by the contour and minimum wall thicknesses between inner cooling channel and outer diameter of drill, between inner cooling channel and rake surface and between inner cooling channel and chip clearance, which are in a range between a lower limit and an upper limit, where the lower limit is 0.08 × D for D <= 1 mm and 0.08 mm for D> 1 mm, in particular 0.08 × D for D <= 2.5 mm and at 0.2 mm for D> 2.5 mm, preferably at 0.08 × D for D <= 3.75 mm and at 0.3 mm for D> 3.75 mm, for example at 0.1 × D for D <= 3 mm and at 0, mm for D> 3 mm, and wherein the upper limit is 0.35 × D for D <= 6 mm and 0.4 × D-0.30 mm for D> 6 mm especially at 0.333 x D for D <= 6 mm and at 0.4 x D-0.40 mm for D> 6 mm, preferably at 0.316 x D for D <= 6 mm and at 0.4 x D-0 , 50 mm for D> 6 mm, more preferably 0.3 × D for D <= 6 mm and 0.4 × D-0.60 mm for D> 6 mm, for example at 0.2 × D or 0.15 × D for D <= 4 mm and at 0.6 mm for D> 4 mm.

With the experimentally determined Cooling duct geometry and location of the cooling channel in particular, on the dock surprising in their magnitude positive results are achieved:

It turned out that at the tool with inventive cooling channel profile across from a trine shape at equal or higher throughputs Load dramatically lower local voltage loads occur. The corresponding higher Strength values of the insert tool according to the invention were confirmed in fracture tests. The experiments were with tools made of a common carbide with Values of the 0.5-bis 0.85 times the radius of a circle enclosed by the contour for the narrowest radius of curvature carried out. Values of 0.6 to 0.85 times appeared particularly suitable, in particular from 0.7 to 0.8 times the diameter of the enclosed one Circle. For example, a drill came with one Nominal diameter of 4 mm a minimum radius of 0.75 × diameter of enclosed circle on the side facing the flute of the cooling channel approx. 35% lower voltage peaks with the same cooling channel cross-sectional area. Thereby could a value of only 0.3 mm for the local minimum wall thickness be achieved with a sufficient drill strength. For tools from a different material but even values in a range of 0.35 - 0.9 × circle radius make sense. at Use of a higher material ductility and thus higher Stress in particular tensile stress resistance, for example, still minimum radii of curvature down to 0.35 × circle radius of the enclosed circle provide advantageous results. Also For tools that are exposed to special stress conditions can Such a dimensioning makes sense.

Besides the lower notch stresses because of the ratio to conventional Trigonprofilen relatively gentle rounding occurs while the additional Effect that the location of the cooling channel contour on which the greatest curvature is applied, from the point where the wall thickness of the web is the lowest, is offset. It follows that the wall at the highest loaded Place relatively thick and thus unbreakable.

On the other hand, the throughputs increase in an insert tool with the cooling channel geometry according to the invention compared to a Insert tool with round cooling channel geometry almost proportional to the cross-sectional area, with the increase in the Notch stresses with increasing cross-sectional area in the region of the cooling channel geometry according to the invention compared to the conventional ones Trigonprofilen surprising is small. With the cooling channel profile according to the invention can be so cross-sectional areas realize that with a round profile with the same coolant throughput due to too low wall distances would lead to a failure of the tool.

The result was a connection of the sufficient wall thickness to the nominal diameter, which takes place with small tool diameters linearly with an increase in the tool diameter. This is already at this point on the 12 to 14 which shows in diagram form the lower limit and the upper limit for the minimum wall thickness respectively above the nominal diameter of the tool. Thicknesses with an extremely high coolant supply have proven to be wall thicknesses above a lower limit of 0.08 × D for D <= 2.5 mm and 0.2 mm for D> 2.5 mm, preferably at 0 , 08 × D for D <= 3.75 mm and at 0.3 mm for D> 3.75 mm, for example at 0.1 × D for D <= 3 mm and at 0.3 mm for D> 3 mm lie, where D denotes the nominal diameter. For example, the above-mentioned 4 mm nominal diameter drill bit tested had a wall thickness of 0.3 mm.

Already with such small wall thicknesses due to the stress distribution in the tool bar cheap Cooling channel contour design according to the invention high tool strengths and thus achieve service life. In individual cases it may even be sufficient, minimum wall thicknesses of 0.08 mm for Diameter from 1 mm to provide.

On the other hand, the minimum wall thickness only through the desired Throughput limited to the top. Here were values of 0.35 × D for D <= 6 mm and 0.4 × D-0.30 mm for D> 6 mm, in particular from 0.333 × D for D <= 6 mm and 0.4 × D-0.40 mm for D> 6 mm, preferably from 0.316 × D for D <= 6 mm and from 0.4 × D-0.50 mm for D> 6 mm, particularly preferred of 0.3 × D for D <= 6 mm and 0.4 × D-0.60 mm for D> 6 mm, for example of 0.2 × D or 0.15 × D for D <= 4 mm and 0.6 mm for D> 4 mm as appropriate maximum values out to which a cooling channel contour according to the invention makes sense.

It had been shown that the cooling channel geometry according to the invention especially for smaller tools, which are particularly on a respect Strength and coolant flow optimized space utilization on the tool bar arrives, suitable is. This finding was made by the upper limits according to the invention for the Minimum wall thicknesses taken into account above a certain Nominal diameter stronger increase than in the range of smaller diameter values.

In particular, it has been found that from diameters of 6 mm, a linear increase of the cooling channel cross-sectional areas with the nominal diameter only in individual applications, such as in deep hole drills, makes sense, since the need for lubricant can be covered even under proportionally growing cooling channel cross sections. Of course, it may also be useful for larger diameter values to approach the minimum wall thickness up to the lower limit according to the invention with sufficient strength to achieve a high coolant supply.

The values according to the invention for the upper limit of the minimum wall thicknesses take into account this consideration, wherein the inventive design the cooling channel contour especially at minimum wall thicknesses in the range below 0.2 × D useful is. Especially in the minimum wall thickness range below 0.15 × D for D <= 4 mm and 0.6 mm for D> 4 mm proves by the inventive shape and Sizing of the cooling channels related on the available standing space achieved flow increase while at the same time good tool strength as surprising Cheap.

It was, however, taken into account that often tools of different diameters from blanks, in particular sintered blanks of the same diameter are manufactured. The sintered blanks are common as cylindrical rods formed with already molded cooling channels. That is, for example, a blank having a raw diameter of 6.2 mm tools with nominal diameters of 4 mm, 5 mm and 6 mm be made. For the 6 mm tool with the same cooling channel as with the 4 mm tool would be therefore the minimum wall thickness between cooling channel and tool circumference 1 mm larger. Under This manufacturing aspect also includes upper limits for the Wall thickness of 0.35 × D for D <= 6 mm and 0.4 × D-0.30 mm for D> 6 mm, in particular from 0.333 × D for D <= 6 mm and 0.4 × D-0.40 mm for D> 6 mm, preferably from 0.316 × D for D <= 6 mm and from 0.4 × D-0.50 mm for D> 6 mm, particularly preferred of 0.3 × D for D <= 6 mm and 0.4 × D-0.60 mm for D> 6 mm still in one area, in which the cooling channel geometry according to the invention Benefits.

At this point it should be mentioned that the minimum wall thicknesses between cooling channel and drill outer circumference, or clamping surface or Spanfreifläche Of course chosen differently can be. In terms of strength, it comes in particular to the minimum distance or the minimum wall thickness between the cooling channel and rake surface to that, therefore, opposite the minimum wall thickness between cooling channel and chip clearance be chosen larger can. Also opposite the minimum wall thickness between cooling channel and drill outer circumference can the minimum wall thickness between cooling channel and rake surface provided with larger values be to the higher strength requirement Take into account. On the other hand, it can, for example, under the above, in practice relevant manufacturing aspect of the blanks same diameter for Tools of different diameters to a minimum wall thickness between cooling channel and drill outer circumference come, which is bigger as the one between the cooling channel and rake surface.

According to the invention, it is thus possible overall, the available space on the web or bars of a rotating Cutting tool so that unmatched high coolant throughput and strength values are achieved. Because of the shape of the Cooling channel contour can extremely small wall thicknesses be provided, despite extreme coolant flow rates a sufficiently high strength of the tool is effected overall.

The proposed cross-sectional geometry is equally suitable for drills, Rubbing and milling, for example, end mill. It should be mentioned that the cooling channel geometry according to the invention even with stepped tools, such as step drills, advantageous can be used. The specified nominal diameter therefore refers in this case, on the tool diameter at the tool tip or on the diameter of the pilot hole.

Drill with the cooling channel profile according to the invention can both in the load case of attacking compressive forces and Torques typical for drilling as well as shear forces or bending moment load, as they occur when entering the workpiece occur, high load values non-destructive over long Endure life. Similar lateral force and bending stresses also occur in Gleich- or Mating cutters on. On the other hand, the achieved coolant flow rate is Amount and pressure drop over the tool length high standards just.

Due to the low notch stresses in the cooling channel geometry according to the invention is it possible, on the one hand, with the same wall thicknesses compared to conventional insert tools much improved stability at least approximately same throughputs or on the other hand, the minimum wall thickness between cooling channel and rake surface to dimension smaller, resulting in the cooling channel cross-section and thus the throughput increases accordingly.

To an increased coolant flow at reduced Carries pressure drop The effect of this is that due to the large radii a cheaper hydraulic radius, i. one with respect to the enveloping lateral surface of the cooling channel size Cross sectional area of the cooling channel results. The average flow rate, the essential from the pipe frictional force and the drag caused by the pressure drop depends is so opposite the conventional one Trigon profiles higher, so that with the same cross-sectional area, a higher throughput is achieved.

The cooling channel geometry according to the invention is particularly suitable for tools in which the conflict between sufficient coolant supply on the one hand and sufficient strength on the other hand is particularly problematic, usually for tools with small diameters and / or large tool length. According to the advantageous development according to claim 2, the nominal diameter is in the range of 1 mm to 25 mm, in particular 1 mm to 16 mm. Particularly large are the advantages of the invention Kühlka However, nalgeometrie for even smaller tools whose nominal diameters are in a range of 1 mm to 12 mm, in particular in a range of 1 mm to 6 mm.

But also with larger tool diameters can the cross-sectional geometry of the invention in full be for a maximum coolant supply to accomplish, especially in deep hole drilling, in which the coolant is pressed into the internal cooling channels with up to 1000 bar, so enough pressure to provide the chips to squeeze out of the borehole.

The cross-sectional geometry according to the invention is used for example in single-lip drills. Especially advantageous However, it works with two- or multi-bladed tools, there with small web widths also a correspondingly smaller space for the Internal cooling channels is available. The cooling channel geometry according to the invention is also suitable for both straight and coiled or spiral tools.

In the advantageous embodiment according to claim 4 while the two curvature maxima of the cooling channel cross section on the same radial coordinate that is greater than or equal to the radial coordinate of the cooling channel cross section enclosed circle is. According to claim 5 is the applied Radius at the two curvature maxima equal; according to claim 6 is the cooling channel cross section to a radially extending axis of the drill axis symmetrical. These developments bear the essentially symmetrical shape the tool bars and thus of the observance of the experimental determined Minimum wall thicknesses available standing space for the cooling channel cross section on the jetty bill. But that would be wrong also - in particular when the web widening in the radial direction on the side of the main cutting edge faster than on the web-facing side - an unbalanced Shape of the cooling channel cross sections conceivable, around the available standing space optimal use. Also from the aspect that the highest Load on the main cutting edge facing the cooling channel occurs while on the steg back facing side relatively withstand lower loads must, can unbalanced designs are considered.

It has proven to be particularly advantageous if the cooling channel has the shape of an ellipse in cross-section according to claim 7. Preferred values for the ratio ellipse main axis / minor axis are 1.18 to 1.65, particularly preferably 1.25 to 1.43, for example 1.43. An ellipse in the sense of the invention is not only a mathematically exact ellipse (x ² / a ² + y ² / b ² = 1), but also a production-related, ie approximated ellipse: In straight-grooved HSS drills, an ellipse with a large ellipse Cooling channel cross-section may still be milled. In this case, with an end mill having the smallest radius of the ellipse, an ellipse-like bore in the tool bridge is created by moving - starting from the smallest radius - at the maximum curvature with diameter expansion to the largest radius at the minimum curvature. The radii do not change steadily, but only in the area of the transition from the largest radius to the smallest radius, while the smallest radius is maintained over a non-zero length at the maximum of curvature.

Not only tools with coiled cooling channels but are preferably made of hard metal, for example, based on tungsten carbide. The plasticized mass for extrusion molding is thereby produced under constant through-rolling from a hard metal powder with the addition of a binder, for example cobalt, and a plasticizer, for example paraffin. Also, the use of ceramic or cermet and other sintered materials in which the cooling channel cross-sectional geometry before the tool hardens - for example, in an extrusion process - can be defined in the still soft raw material, are possible. To this will beipielhaft to the above-mentioned font DE 42 42 336 A1 directed. It would theoretically also be conceivable for spiral tools, tools made of high-speed steel (HSS) or similar. To equip steels with the Kühlkanalquerschnittsgeomterie invention, for example with a laser sintering process.

Another extrusion process, that for the production of helical tools with the cooling channel geometry according to the invention is also mentioned here:

The plasticized mass flows in an extrusion head, at first substantially twist-free in a nozzle tip to there along the longitudinal axis at least one, at the nozzle firmly attached pin to the outlet opening of the nozzle and through to be pressed through them. The nozzle has a circular cylindrical, preferably substantially smooth surface, so that the resulting Blank has a fully cylindrical outer contour. The streamed pen is non-rotatable on the nozzle mandrel held. The flow in the Nozzle mouthpiece becomes on the one hand by the slope of the helices of the pen and on the other hand by a rotating portion of the nozzle tip a Radial component induced.

As a result, a total helical flow is achieved, which takes place when tuning the rotational speed of the rotating section on the slope of the helical shape of the protruding into the nozzle orifice pin so that the flow of the extruded mass of the spiral pitch substantially follows, ie that the particles at the radial height of Pen have a the direction of the pen entprechende flow direction, whereby a bending deformation of the pin or in spite of its position and rotationally fixed arrangement can be avoided. Also, a plastic deformation of the extruded mass or an un uniform structure or density distribution in the mass can be avoided, since the radial component of the flow is not forced by Verdralleinrichtungen or deflectors such as vanes, etc., but is achieved solely by the rotational movement of the rotatable portion of the nozzle tip. The radial movement of the flow is thus not caused by deflection of an obstacle standing in the way of the flow, but solely on the friction forces inherent in the extruded mass, which cause the mass to be taken by the rotational movement of the nozzle portion, wherein the thus induced rotational movement of the Starting nozzle wall independently propagates towards the interior of the nozzle until a stationary helical flow sets, in a dependent of the shear stress and thus the viscosity and toughness of the extruded mass ratio.

It thus comes to a large extent Tension of the extruded mass freed from tensions and density inhomogeneities, so that after the ejection of the blank from the nozzle also no subsequent Aufzwirbeln as in a forced by a Verdralleinrichtung helical flow to fear is. With the method according to the invention can thus be green produce with high helix accuracy.

For elliptical cooling channel cross sections can the cooling channel due to the low notch stresses at the curvature maxima with a smaller one Minimum wall thickness between cooling channel and main cutting edge are dimensioned as in designs in which the curvature maxima radially further outwards verszt are, since there are tighter radii than in the elliptical Design.

In addition to the elliptical cooling channel shape But there are also others, especially in manufacturing technology Regarding advantageous tool designs in which the cooling channel contour does not describe an ellipse.

Especially with coiled tools results from a cooling channel geometry according to claim 8, in which the maximum curvature across from the center of the enclosed circle offset outwards are, under manufacturing aspects an easier controllability of the manufacturing process used in the extrusion process Pins that specify the spiral helix of the internal cooling channels. Because when extruding are coiled to make the cooling channels Pins are used, which are arranged on a mandrel in front of an extrusion die are and so in the oncoming Mold the cooling channels. while the Producing elliptic coiled pins is relatively expensive, is the production of coiled pins with offset outwards curvature maxima due to the relatively large contour sections on the inside of the wires, which are available for precise fitting on a drawing mold, comparatively easy.

Particularly advantageous in this regard it is when the radially inner side of the cooling channel contour rectilinear leg sections, where the wires at Can safely support coils in the drawing form.

From experiments and simulations was clearly that even with such cooling channel cross sections similar good Achieve results in terms of notch stress and coolant flow rate let as with elliptical cooling channel cross-sections, as long as enough size Minimum radii and wall thicknesses are maintained. Due to smaller Radii at the maximum of curvature however, as with the elliptical shape, the minimum wall thicknesses are greater.

Leave the features of the claims to combine as much as it pleases.

It should be emphasized that as a material for the Drills all common Materials of modern high performance drills, e.g. HSS high-speed steel, but especially all carbide grades. Besides Also suitable are ceramic, cermet or other sintered metal materials for the inventive tool.

Moreover, the tool can with usual Coatings be equipped, at least in the area sharp cutting. If it is a hard material layer, this is preferably thin executed wherein the thickness of the layer is preferably in the range between 0.5 and 3 μm lies.

The hard material layer consists for example of diamond, preferably monocrystalline diamond. However, it can also be embodied as a titanium-nitride or as a titanium-aluminum-nitride layer, since such layers are deposited sufficiently thin. But also other hard material layers, for example TiC, Ti (C, N), ceramics, eg Al ₂ O ₃ , NbC, HfN, Ti (C, O, N), multi-layer coatings of TiC / Ti (C, N) / TiN, multilayer coatings Ceramic coatings, in particular with intermediate layers of TiN or Ti (C, N), etc. are conceivable.

Additionally or alternatively, it is also possible to use a layer of soft material which is present at least in the region of the grooves. This soft coating preferably consists of MoS ₂ .

The following are schematic Drawings preferred embodiments closer to the invention explained.

1 shows a cross-sectional view of a double-edged drilling tool, wherein a plurality of cooling channel contours are drawn according to the invention in order to illustrate the scope of the invention;

2 shows an isometric view of a drilling tool with one of the in 1 shown embodiments of the cooling channel;

3 shows a cross-sectional view of a double-edged drilling tool, wherein on the upper web a conventional trigonal cooling channel contour is eigzeichnet, one on the lower web inserted a distinguished cooling channel contour according to an embodiment of the invention is compared;

4 shows an isometric view of a drilling tool with the in 3 shown embodiment of the cooling channel;

5 shows a cross-sectional view of a double-edged drilling tool, wherein on the upper web a conventional trigonal cooling channel contour eigzeichnet is compared with a drawn on the lower web cooling channel contour according to another embodiment of the invention;

6 shows an isometric view of a drilling tool with the in 5 shown embodiment of the cooling channel;

7 shows a cross-sectional view of a double-edged drilling tool, wherein on the upper web a conventional trigonal cooling channel contour eigzeichnet is compared with a drawn on the lower web cooling channel contour according to another embodiment of the invention;

8th shows an isometric view of a drilling tool with the in 7 shown embodiment of the cooling channel;

9 shows a cross-sectional view of a double-edged drilling tool, wherein on the upper web a conventional trigonal cooling channel contour eigzeichnet is compared with a drawn on the lower web cooling channel contour according to another embodiment of the invention;

10 shows an isometric view of a drilling tool with the in 9 shown embodiment of the cooling channel; and

11 Finally, a comparable tool with common trigonförmiger Kühlkanalquerschnittsgeometrie can be seen;

12 shows a diagram in the lower limits W _{min, 1} , W _{min, 2} , W _{min, 3} , W _{min, 4} according to the invention for the minimum wall thickness between the cooling channel and Bohreraußenumfang (d _AUX ), cooling channel and rake face (d _SPX ) and cooling channel and Spanfreifläche (d _SFX ) are applied over the drill nominal diameter;

13 shows a diagram in which the inventive upper limit W _{max, 1} , for the minimum wall thickness between the cooling channel and Bohreraußenumfang (d _AUX ), cooling channel and rake face (d _SPX ) and cooling channel and Spanfreifläche (d _SFX ) over the Bohrernenndurchmesser is plotted;

14 ₂ shows a diagram in which the upper limits W _{min, 1} , W _{min, 2} , W _{min, 3} , W _{min, 4} , W _{max, 5} , W _{max, 6} for the minimum wall thicknesses between the cooling channel and outer diameter of the drill (d _AUX ), Cooling channel and rake surface (d _SPX ) as well as cooling channel and chip clearance surface (d _SFX ) above the nominal drill diameter are indicated;

First, reference is made to 1 showing a cross-sectional view of a double-edged, two-jaw drill 2 and two flutes 1 can be seen. At the cutting side, the webs are each by a chip surface 5 limited, on the non-cutting side by a chip clearance 6 , The outer circumference of the drill is the reference numeral 7 assigned. Starting from a drill core with diameter d _K spread surface 5 and chip clearance 6 the footbridges 2 to such a web width, that the nominal diameter D of the drill is achieved. The webs are approximately symmetrical to a web center line S, which is located radially to the drill axis A. On the symmetry line S are on the lower bridge 2 the center M of a circle K, which is completely within the cross-sectional area of the local cooling channel bore 3 located. On the upper web is the center M '' of the local circle K with the same diameter 2R ₀ slightly away from the rake face to the rear completely within the cross-sectional area of the local cooling channel bore 3 ,

In this case, a plurality of the cooling channel contours surrounding the respective cooling channel 30 . 31 . 32 according to different embodiments of the invention compared to each other: At the lower web is an elliptical contour 30 for the cooling channel 3 drawn with a solid line, another contour 31 for the cooling channel 3 with dashed line. At the upper bridge is a contour 32 for the cooling channel 3 drawn with dashed line.

The cooling channel contours 30 . 31 have a symmetrical to the symmetry shape, while the cooling channel 32 deviates only on the non-cutting side of the predetermined by the touching enclosed circle K contour. The curvature radii R ₁ , R ₁ 'and R ₁ "are in each case at the curvature maxima, the contours 30 . 31 each have two equally curved curvature maxima, while at the contour 32 only a maximum curvature radius R ₁ '' is present.

It can be seen that with the cooling channel cross-sectional geometry according to the invention while maintaining the same distance to the core diameter d _K , the cooling channel holes having a circular diameter 2R ₀ , a substantial increase in passage area can be achieved in the areas of the cooling channel facing the rake face or the chip flank face.

In this case, the passage surface extraction is limited only by the minimum wall thicknesses to be complied with, for the sake of clarity, only for the breaking strength of the drill particularly important minimum wall thickness d _SPE , d _SPA and d _SPA '' between the cooling channel 3 and rake surface 5 for each of the cooling channel contours 30 . 31 . 32 is drawn.

The minimum wall thicknesses are again determined by the minimum strength that the drill is to achieve given and thus by the radii R ₁ , or R ₁ 'or R ₁ ''at the maximum curvature of the respective cooling channel contour 30 . 31 . 32 , This is reflected in the fact that for the elliptical cooling channel contour 30 a smaller minimum wall thickness d _SPE than for the cooling channel contours 31 . 32 with outwardly offset curvature maxima (minimum wall thickness d _SPA ) can be applied.

Keep the cooling channel contours 30 . 31 the minimum wall thickness d _SPE or d _SPA between cooling duct 3 and rake surface 5 a, which is essentially the (unnamed) minimum wall thickness between the cooling channel 3 and chip clearance 6 equivalent. By contrast, the contour 32 exemplarily on the rake face 5 facing side a larger minimum wall thickness d _SPA '' on than on the rake face 5 opposite side. Because on the one hand, the center M 'of the enclosed circle is offset away from the cutting side, on the other hand, the cooling channel contour 32 only on the chip free surface 6 A maximum curvature of curvature (radius R ₁ ") on the side facing the curve of the cooling channel contour 32 makes it clear, however, that within the scope of the invention, cooling channel cross sections are also conceivable in which the maximum curvature lies on the side facing the rake face.

2 shows an isometric view of a coiled drilling tool with an elliptical cooling channel cross-sectional contour 30 , The tool points to his by the flutes 1 separated two webs 2 one main cutting edge each 4 on. The flutes 1 and footbridges 2 run at a helix angle of approx. 30 ° to a drill shaft designed as a solid cylinder 9 on which the tool can be clamped in a tool holder or in a chuck. The internal cooling channels 3 extend through the entire tool and are twisted at the same spiral angle as flutes 1 and footbridges 2 ,

For particularly high loads sets while drilling tools made of solid carbide, which has a high compressive strength, Torsion resistance, hardness and wear resistance. Such high performance tools are also able to cope with the high loads, for example at hard machining, dry machining, minimum quantity lubrication MMS and high-speed machining HSC occur. Also It has been recognized that the objectives are MMS capability and significantly higher cutting performance not in opposite directions but can be realized at the same time. Drilling tools for use were developed with MMS, run for example, with much higher feeds than Tools for conventional cooling lubrication. Here comes the supplied Amount of coolant a crucial role too.

In so-called high-performance cutting (HPC) method is tried today taking into account all involved Process parameters to further reduce manufacturing costs. For tools are besides the production costs mainly the main times and Service life is crucial, which in turn crucially depends on the mobile Depend on feed rate and thus of existing machine tools / high performance spindles Generable speeds.

The feed rate is not only limited by the speed, but on the one hand also by the fact that it must be ensured that no chaff accumulation during chip removal. In contrast to straight grooved tools - in this regard is on the 4 . 6 . 8th and 10 directed - has that in 2 illustrated coiled tool thereby decisive advantages. Because the coiled design allows easier removal of the mixture of chips and lubricant. At the in 2 The tool is shown, the coolant is introduced to a large extent directly into the flute, since the exit surface of the cooling channels 3 over both sections of the open space divided by a so-called four-surface bevel 13 extends, so that a large part of the coolant flows directly into the flute. To further improve the chip removal flow, it would also be conceivable to design the flute such that it widens from the drill tip to the drill shank. Also with regard to centering coiled tools are advantageous because these tools can be supported over its entire outer circumference in the hole. This in 2 For this purpose, the tool shown has a support phase beginning at the cutting corner 11 on.

On the other hand, the tensions in the tool no over rise to a beaten level, otherwise breakage or signs of wear occur. Here too shows that the design of the cooling channels is a decisive criterion for the Usability of the drill is.

Finally, the inventive cooling channel geometry found through various experiments. In each case a series except for the cooling channel geometry uniform Tools with the same nominal diameter one of compression and torsion shares subjected to existing stress and the voltage peaks occurring at the Kerbgründe, i.e. the curvature maxima the cooling channel cross section contours determined.

For example, six double-edged, grooved drill with
Nominal diameter D = 4 mm, and linear web widening, ratio web width to groove width 1: 1,
with a
Compressive force of 860 N and a torsional moment of 0.8 Nm
applied. These drills are the 1 and 3 to 11 refer to.

The drill with a circular cooling channel profile is the 1 (Cooling channel contour follows everywhere the enclosed circle with radius R ₀ ). Four drills with inventive cooling channel contour are in the 3 to 10 shown on an enlarged scale. Each of the cooling channel profiles shown 30E ( 3 . 4 ) 30I ( 5 . 6 ) 30II ( 7 . 8th ) and 30III ( 9 . 10 ) includes the circle with radius R ₀ touching. In this case, the same features with the same reference numerals as in 1 named.

In the 4 . 6 . 8th and 10 In each case, a drill according to an embodiment of the invention is shown in an isometric view. The drills each have straight flutes 1 and footbridges 2 with guide bevels 11 . 12 on the side of the main cutting edge 4 and on the main cutting edge 4 on the opposite side. Through the drills run through cooling channels 3 from the drill bit 8th to the opposite end of the drill bit on the drill shank 9 , The cooling channels 3 occur at the unspecified open space of the drill, the back by a Ausspitzung 10 is limited to Querschneidenverkürzung. The Figs. 3 . 5 . 7 and 9 show a drill cross section of the in Figs. 4 . 6 . 8th and 10 shown drill, wherein an inventively designed cooling channel on the lower drill bit for comparison purposes on the upper drill bit each a cooling channel was compared with conventional Trigonprofil.

A drill with conventional cooling channel trigon profile with the same inscribed circle with radius R ₀ is in 11 shown in isometric view. In the cross-sectional views of 2 . 4 . 6 . 8th Such a designed cooling channel profile is in each case contrasted with a cooling channel profile designed according to the invention.

With d _SPX , d _SFX and d _AUX , the minimum wall thicknesses between the cooling channel are always the same 3 and rake surface 5 , Cooling channel 3 and chip clearance 6 as well as between cooling channel 3 and outer circumference 7 denotes, with R _1X and R _2X respectively the smallest and the largest voltage applied to the cooling channel contour radius, where X stands for E, I, II, III. The corresponding sizes in the trigonal Kühkanalprofil were designated D _SPT , D _SFT and D _AUT .

For the cooling channel profiles the following values were used:

• - Circular cooling channel profile with R ₀ = 0.4, 1
• - Elliptic cooling channel profile 30E with main axis 2a = 0.55 mm, minor axis 2 B = 0.4 mm, Figs. 2 and 3 ;
• - Approximately elliptical cooling channel profile 30I with the narrowest radius R _1I = 0.3 mm, R _2I = 0.6 mm, Figs. 4 and 5 ;
• - Approximately elliptical cooling channel profile 30II with narrowest radius R _1II = 0.3 mm, widest radius R _2II = 0.5 mm, Figs. 6 and 7 ;
• - Approximately elliptical cooling channel profile 30III with narrowest radius R _1III = 0.2 mm, widest radius R _2III = 0.5 mm, Figs. 8th and 9 ;
• - Triangular cooling channel profile, narrowest radius R _1T = 0.1 mm, widest radius R _2T = 0.4 mm, 10 and Figs. 2 . 4 . 6 . 8th ,

The cross-sectional area of the cooling channel in circular form is significantly smaller than that in the other cooling channels, while the remaining cooling channels have almost the same cross-sectional areas: Circularity: 0,50 mm ² profile 30E : 0.69 mm ² profile 30I : 0.63 mm ² profile 30II : 0.67 mm ² , profile 30III : 0.66 mm ² trigon: 0.65 mm ² .

In the evaluation of the maximum voltage peaks on the chip surface 5 the curved maximum (at a distance of 0.25 × D to the main cutting edge), the particular advantages of the embodiments according to the invention become clear. The cooling channel profiles according to the invention have significantly lower stress values in the case of approximately the same or even greater cross-sectional area than in the case of the trigonprofile, while the surface profile exhibits strong area increases with simultaneously underproportionally increasing stress peaks: Circular profile: 700N / mm ² ; profile 30E : 980 N / mm ² ; profile 30I : 1034 N / mm ² ; profile 30II : 1031 N / mm ² ; profile 30III : 1133 N / mm ² ; Trigon profile: 1520 N / mm ² .

It can be seen that the Trigon cooling channel with optimal utilization of a pie-shaped space with a large cross-sectional area, the same minimum wall thickness is achieved as in the circular cooling channel profile. However, exorbitant high voltage peaks (1520 N / mm ² ) occur, so that the risk of breakage is significantly higher, or the service life of the tool drops disproportionately.

With regard to the voltage peaks at the cooling channel, a voltage spike at the notch base, which is about 25% -35% lower than the trigonform, results for the cooling channel profiles according to the invention. The closer is approximated to the trine profile, the more the voltage spikes rise. However, this increase does not occur linearly, but exponentially, so that also with the profile 30III good values can still be achieved. At the profiles 30E . 30I and 30II however, almost identical voltage peaks were observed at approximately equal cross-sectional areas.

In this case, all the cooling channel contours shown in the range of 8% -11% of the nominal diameter of the tool between chip flute and chip clearance area were observed. The wall thickness between the cooling channel and chip clearance was 8% × D at the contour 32 ( 1 ) especially small. At the lower jetty of in 3 shown tool is, however, drawn with a dashed line the outer contour of a slightly larger tool. The drawn in dashed Liie tool is made from the same blank as the tool shown by a solid line. The shape, position and dimensions of the cooling channel 3 are the same. However, the slightly larger tool has a minimum _{wall thickness} d _{AUE '} between the cooling channel 3 and outer circumference 7 ' which is more than 20% larger than the minimum _{wall thickness} d _AUE .

Even with smaller nominal diameters D, the effect of the invention was shown. For example, drills with a nominal diameter D = 1.2 mm, which are geometrically similar to the above-described drills with D = 4 mm, were also subjected to a load test. In each case, a torsional moment of 0.026 Nm and a compressive force of 52 N was applied to the drills. The drills had the following cooling channel geometries: circular cooling channel with R ₀ = 0.12 mm and area 0.045 mm ² ; elliptical cooling channel with a = 0.085, b = 0.06, area 0.065 mm ² ; trigonic cooling channel with R ₁ = 0.04 mm, R ₂ = 0.16 mm, area 0.07 mm ² ;

Again, the maximum stress at the maximum curvature - measured 0.25 × D behind the main cutting edge - was exorbitantly higher in the trigonprofil with 1480 N / mm ² than in the circular profile with 660 N / mm ² , while the drill with elliptical cooling channels with a large cross-sectional area with a value of 950 N / mm ² bearable voltage peaks occurred.

In the 12 Values according to the invention for the lower limit W _{min of} the minimum wall thicknesses over the diameter D are plotted. The tools according to the invention in this case have minimum wall thicknesses d _AUX , d _SPX , d _SFX on the left or on the left of the graph W _{min, 1} , in particular left of the graph W _{min, 2} , preferably left of the graph W _{min, 3} , for example left of W _{min, 4} lie.

The course of the upper limit W _{max, 1} for the minimum wall thicknesses d _AUX , d _SPX , d _SFX is in 13 plotted over the nominal diameter D. In 14 this course is compared to the preferred upper limits W _{max, 2} , W _{max, 3} , W _{max, 4} W _{max, 5} and W _{max, 6} .

Of course, deviations from the variants shown possible, without leaving the basic idea of the invention.

In particular, cooling channel contours would be conceivable at the radii at the maximum curvature on the rake surface facing side of the cooling channel greater than on the Spanfreifläche facing side.

Also, the invention is not on coiled or straight grooved single or multi-bladed tools limited to any tip geometry and groove-web ratio, at which the cutting edges are located directly on the tool head, but can also be used with tools with screwed or soldered inserts or interchangeable inserts and tools on the shaft soldered Cutting part or drill head are used.

The invention was based on universal usable cutting tools described. It should be highlighted be that a special field of application is deep hole drilling, wherein the cooling channel geometry according to the invention especially with relatively small nominal diameters the advantages unfolded, even if the tool is a deep hole drilling tool with extremely small ratio From nominal diameter to cutting length is designed.

Claims (11)

Rotary cutting tool, in particular drill, with a nominal drill diameter (D), at least one flute ( 1 ) and at least one footbridge ( 2 ) extending from a tool tip ( 8th ) to a tool shank ( 9 ), wherein at each bridge ( 2 ) a main cutting edge ( 4 ) and an internal cooling channel ( 3 ) formed by the tool tip ( 8th ) extends to an opposite end of the drill and a continuously extending cross-sectional contour ( 30 ; 31 ; 32 ; 30X ), which encloses an imaginary circle (K) with a center point (M), the cross-sectional contour ( 30 ; 31 ; 32 ; 30X ) of the internal cooling channel ( 3 ) has at least one, preferably two maximum curvatures, the distance to the drill axis (A) in the direction of a line between the center (M) and drill axis (A) is greater than or equal to the distance of the center point (M) to the drill axis (A), characterized by minimum wall thicknesses (d _AUX , d _SPX , d _SFX ) between internal cooling channel ( 3 ) and drill outer circumference ( 7 . 7 ' ), between internal cooling channel ( 3 ) and rake face ( 5 ) and between internal cooling channel ( 3 ) and chip clearance ( 6 ), which in one Range between a lower limit (W _{min, 1} , W _{min, 2} , W _{min, 3} , W _{min, 4} ) and an upper limit (W _{max, 1} , W _{max, 2} , W _{max, 3} ) lie, with the lower limit at 0.08 × D for D <= 1 mm and at 0.08 mm for D> 1 mm (W _{min, 1} ), in particular at 0.08 × D for D <= 2.5 mm and at 0.2 mm for D> 2.5 mm (W _{min, 2} ), preferably at 0.08 × D for D <= 3.75 mm and at 0.3 mm for D> 3.75 mm (W _{min, 3} ), for example, at 0.1 × D for D <= 3 mm and at 0.3 mm for D> 3 mm (W _{min, 4} ), and the upper limit at 0.35 × D for D <= 6 mm and at 0 , 4 × D-0.30 mm for D> 6 mm (W _{max, 1} ), in particular at 0.333 × D for D <= 6 mm and at 0.4 × D-0.40 mm for D> 6 mm (W _{max, 2} ), preferably at 0.316 × D for D <= 6 mm and at 0.4 × D-0.50 mm for D> 6 mm (W _{max, 3} ), more preferably at 0.3 × D for D <= 6 mm and at 0.4 × D-0.60 mm for D> 6 mm (W _{max, 4} ), for example at 0.2 × D (W _{max, 5} ) or 0.15 × D for D <= 4 mm and at 0.6 mm for D> 4 mm (W _{max, 6} ), and wherein the radius (R ₁ ; R ₁ '; R ₁ "; R _1X ) at the strongest curvature of the cross-sectional contour ( 30 ; 31 ; 32 ; 30X ) of the internal cooling channel ( 3 ) 0.35 to 0.9 times, especially 0.5 to 0.85 times, preferably 0.6 to 0.85 times, more preferably 0.7 to 0.8 times , For example, 0.75 times the radius of the circle (R ₀ ) corresponds. Cutting tool according to claim 1, characterized by a nominal diameter (D) in the range of 1 mm to 25 mm, in particular 1 mm to 16 mm, preferably 1 mm to 12 mm and particularly preferred 1 mm to 6 mm. Cutting tool according to claim 1 or 2, characterized by its design as a double-cutter or multi-cutter. Cutting tool according to one of the preceding claims, characterized in that the two curvature maxima of the cross-sectional contour ( 30 ; 31 ; 32 ; 30X ) of the internal cooling channel have the same radial coordinates. Cutting tool according to one of the preceding claims, characterized in that the radius of curvature (R ₁ ; R ₁ '; R ₁ ''; R _1X ) at the two curvature maxima of the cross-sectional contour ( 30 ; 31 ; 32 ; 30X ) is equal to. Cutting tool according to one of the preceding claims characterized in that the cooling channel cross-sectional area for Line between drill axis (A) and center (M) is symmetrical. Cutting tool according to one of the preceding claims, characterized by an elliptical profile of the cross-sectional contour ( 30 ; 30E ) of the internal cooling channel ( 3 ) on a from the line between the drill axis (A) and center (M) from the rake face ( 5 ) side and / or one to Spansspifche ( 6 ), wherein the aspect ratio of a major axis (a) to a minor axis (b) of the ellipse is in the range of 1.18 to 1.65, preferably 1.25 to 1.43, for example 1.33. Cutting tool according to claims 4 to 6, characterized in that the cross-sectional contour ( 31 ; 32 ; 30I ; 30II ; 30III ) of the internal cooling channel ( 3 ) Has a maximum curvature whose distance from the drill axis (A) in the direction of the line between the drill axis (A) and the center (M) are greater than the distance of the center point (M). Cutting tool according to claim 8, characterized in that the cross-sectional contour ( 32 ; 30 ;) of the internal cooling channel ( 3 ) on the rake surface ( 5 ) facing side and / or the Spanfreifläche ( 6 ) facing side radially within the curvature maxima has a rectilinear portion. Cutting tool according to claim 9, characterized in that the rectilinear sections parallel to the chip surface ( 5 ) or to Spanfreifläche ( 6 ). Cutting tool according to one of claims 1 to 10, characterized by the training as Tieflochbohrwerkzeug with a relationship from nominal diameter (D) to cutting part length in the range of 1: 5 to to 1: 200.